by RTR on Sun Apr 22, 2012 6:20 am
Their are multiple forms of filtration - mechanical, biological. and chemical being the basic types. Biological filtration frequently use specialized media to house the beneficial nitrification bacteria all tanks require. Some tanks are label "filterless" or "natural" but they still do have biofiltration bacteria, just disseminated on various tank surfaces.
Specialized media, such a Pufferpunk suggests (above) is the commonest format and is effective.
HTH
Where's the fish? - Neptune